GETTING READY
1) Remove the skin off the onions and chop. Place aside.
2) Thoroughly wash the celery and slice. Keep aside.
3) Slice the gammon or bacon. Place aside.
4) In a small bowl, dissolve cornflour in little water. Place aside.

MAKING
5) In a pan, melt butter over medium heat.
6) Add onion, celery and gammon or bacon to cook by covering, until onion is translucent and not brown.
7) Stir in lemon rind and juice, wine and stock.
8) Increase heat to bring a boil.
9) Cover with a lid and simmer for 15 minutes by reducing the heat.
10) Add mushrooms and return to the boil.
11) Add the cornflour mixture and season with salt and pepper.

SERVING
12) Just before serving, dilute the sauce in half as much milk and garnish with cream or top of the milk. Pour over meat in a casserole.

TIPS
For a really rich sauce, beat an egg into 125 ml (1/4 pint) single cream and add before serving.